Can Getting Pregnant on the Pill Hurt Your Baby?

You're pregnant. (Hooray!) But you were still on the birth control pill when you found out. (Oh no.)

Relax. You're probably worried about what risks there might be to your baby. Otherwise, you wouldn't be reading this. But here's the info -- and the reassurance -- you need:

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Getting pregnant while on the contraceptive pill, even if you've been on it for years, is most likelyno big deal.

The hormones in birth control pills mimic natural hormones found in your body, explains Sally Rafie, PharmD, a medication safety specialist for the UC San Diego Health System and founder of Choose Control, which offers web-based pharmacy expertise for family planning. "Similar to hormones during pregnancy, birth control pills work by preventing the surge of luteinizing hormone that causes ovulation, so no egg is released," says Rafie. "They also thicken the cervical mucus to prevent sperm from entering the uterus."

Depending on the type of pill you're taking, those synthetic hormones leave your body anywhere from 24 hours to several days, Rafie says. (That's why it's so important to take your pill every day, preferably at the same time.)

Consider this good news, since you won't have to worry about how these hormones affect your baby from here on out. But since you became pregnant while still taking the pill, what effect could those hormones already have had on your baby?

"In one year of taking birth control medication, if a woman got pregnant, her chances of getting ectopic pregnancy is .1%," says Dr. Alexander.

Another extremely rare possibility: hormones from oral contraception may cause fetal genetic defects, particularly in males. "Genitalia is formed very early in pregnancy," Alexander explains. "The urethra in the penis on the shaft [may be] lower or you get ambiguous genitalia, where you can't tell if it's a boy or a girl."

But before you get too upset, consider that a massive 1995 study followed more than 65,000 women who took an oral contraceptive during their first trimester and determined it posed no risk to the baby.

That said, of course, you'll want to stop taking all oral contraception as soon as you get your happy news. Then call your OB/GYN, who may want to schedule a pelvic ultrasound to confirm all is okay.

But remember, when it comes to babies conceived while on the pill, "in most cases, everything is fine," Alexander says.